The 10th Symposium on Global Change Studies

3B.16
EL NINO AND GLOBAL WARMING

Kevin E. Trenberth, Boulder, CO

Preliminary indications are that the first 5 months of 1998 are the warmest on record, and this follows on the heals of 1997 being the warmest year on record. The last ten years are the warmest decade on record. Beginning in April of 1997, a major El Ni�o began and continued until May 1998, and it is known from previous events that a mini global warming is associated with El Ni�o, with highest temperatures typically occurring a few months after the peak in El Ni�o. So this El Ni�o is no doubt contributing to the recent warmth, but the long term record also indicates that much more is going on, namely global warming. But El Ni�o itself has been behaving peculiarly in the past 20 years or so, with the recent El Ni�o as the biggest on record by several measures as just one example of that. Since 1976, there have been more El Ni�os and fewer La Ni�as occurring, including the two biggest El Ni�os on record - the event in 1982-83 was the previous biggest - and the longest on record from about 1990 to mid 1995. Statistically, these changes are sufficiently unusual that something else is going on and influencing El Ni�o, and the main thing we can point to is global warming. So a key question is how is global warming influencing El Ni�o? And how do these things come together to affect how we perceive them in terms of weather? This paper addresses these issues and examines them from the perspective of temperatures, precipitation and the hydrological cycle, and El Ni�o itself

The 10th Symposium on Global Change Studies